1994 K75 Saddlebag Repair

I have an exhaust proximity burn hole in the bottom of my left hard case that I need to repair; it is constructed of PP (polypropylene) plastic. Any one have any suggestions? I plan on cropping out the burn hole, lining the inside of the bag bottom with a suitable material, and then adding a patch to fill in the cropped-out section. I will also be adding a strip of heat reflective material to the bottom of the bag after repairs. Thanks, Viejo

VIEJO said:

I have an exhaust proximity burn hole in the bottom of my left hard case that I need to repair; it is constructed of PP (polypropylene) plastic. Any one have any suggestions? I plan on cropping out the burn hole, lining the inside of the bag bottom with a suitable material, and then adding a patch to fill in the cropped-out section. I will also be adding a strip of heat reflective material to the bottom of the bag after repairs. Thanks, Viejo

Click to expand...

Addendum.... the burn hole is approximately 3" in diameter.

Viejo,

The problem is not your saddlebag.

The problem is your bike. A properly running K75 will not burn holes in the stock saddlebags no matter how fast or how far you are riding.

Possibilities for the problem: After market muffler, missing factory heat shield, bike running too lean. Which one is it?

98lee said:

Viejo,

The problem is not your saddlebag.

The problem is your bike. A properly running K75 will not burn holes in the stock saddlebags no matter how fast or how far you are riding.

Possibilities for the problem: After market muffler, missing factory heat shield, bike running too lean. Which one is it?

Click to expand...

Interesting possibility and not one that I had considered but will definitely look into, thanks.

The bike is fairly low mileage (~24K) with the stock muffler and proper heat shield in place. The bike had been sitting up for about ten years when I got it six or seven months ago (with the burn hole already in place). I am the third owner and I know little or nothing about the riding styles of the previous owners. I did a complete fluid change-out and removed the spark plugs for inspection. Their color was good and there was no signs of heat damage to the electrodes, plug wires and caps were in good shape (bike had been stored indoors and covered). I replaced the plugs as a matter of course with the same range plugs (as per BMW) that were removed. The K75 doesn't have a temperature gauge, just a warning light, so I'll put a temperature sensor to the radiator the next time I get the bike up to temperature.

Being a plain K75 the bike only has the headlight and radiator cowls and not the full fairing that causes some K75's to be massive heat generators

This bike has always been a Central/South Texas bike and it does get HOT here!

Thanks again,

Viejo

Your SIDE CASE repair plan sounds good, but Lee is right. There should be no heat burn issues on a k75 with stock exhaust and stock SIDE CASES mounted correctly. Post some pics of the cases on the bike so we can see what you have going on.

I recall this issue (saddlebag repair) has come up a few times previously on the forum and I think there may have been a recommendation for the type of adhesive(s) to use. Looking at the "similar threads" pane, I think this thread is helpful. In it, there is a link to a WebBikeWorld article on the subject that might prove helpful.

I don't have any personal experience repairing the plastic on mine (replaced more than a few latches and hinges though!). Based on your account, who knows what caused the hole- maybe a one-time "accident" by the PO.. I would note that on the original, Krauser-style" bags on my R80/7 (also a Texas bike), the plastic eventually became discolored and brittle along the bottom on both bags, and a one-inch hole did open up on the bottom of one. I assumed it was from heat exposure over the years. The bike was/is functionally stock, in good shape, runs well (100K+ miles), garage kept... I ended up replacing them about 10-12 years ago. My point being: if the final result of your plastic repair isn't to your liking, I see the bags from 80s and 90/s era of K-bikes for sale used from time-to-time for not too much money.

Good luck!

Repair

Years ago I found what was left of a BMW bag on the side of the road and have used it for repairs ever since. You can cut it up for patches and the material is the same for airhead and K model bags.
I have filled small holes and cracks as well as "gluing" patches using the following method: I use a harsh wood rasp to file off a pile of shavings which I mix in a glass jar with acetone to get a sort of paste. I use that to fill holes and just let the acetone evaporate, sanding afterward to even out the surface.
Patch gluing is as simple. I soften the mating surfaces with the acetone, apply a bit of the "mixture" and clamp it all together, again, waiting for the acetone to evaporate.
I've never seen this melting thing on either of my K75s with a stock exhaust. Is the melted spot above the tip of the muffler? Is it possible that the muffler is bent up a bit at the end?

Viejo,

Pictures of the headers and of the muffler would help to see any unusual hot spots (usually seen by blueing in abnormal locations). Plus showing the clearance between the bag and exhaust.

98lee said:

Viejo,

Pictures of the headers and of the muffler would help to see any unusual hot spots (usually seen by blueing in abnormal locations). Plus showing the clearance between the bag and exhaust.

Click to expand...

I'm currently at home in Hutto, TX. and the bike is in my barn in Utopia, TX. so it will be a while before I can post any pictures but I'll definitely give it a shot.

Thanks to all responders!

Dave

1074 said:

Years ago I found what was left of a BMW bag on the side of the road and have used it for repairs ever since. You can cut it up for patches and the material is the same for airhead and K model bags.
I have filled small holes and cracks as well as "gluing" patches using the following method: I use a harsh wood rasp to file off a pile of shavings which I mix in a glass jar with acetone to get a sort of paste. I use that to fill holes and just let the acetone evaporate, sanding afterward to even out the surface.
Patch gluing is as simple. I soften the mating surfaces with the acetone, apply a bit of the "mixture" and clamp it all together, again, waiting for the acetone to evaporate.
I've never seen this melting thing on either of my K75s with a stock exhaust. Is the melted spot above the tip of the muffler? Is it possible that the muffler is bent up a bit at the end?

Click to expand...

The melted spot is centered over the center of the heat shield and I don't believe there is any distortion in the mounting of the muffler but I'll double check.

Nice fix with the shavings paste!

Viejo

If I'm not mistaken, I thought that the bags on the K75 bikes could also be used on older R bikes also. I was actually surprised by that, but I seemed to to have seen them on the R bikes. Is it possible that the bags were used on some other heat generating machine other than the K75? These bags seem to move from owner to owner.

I'm currently rebuilding a set of used bags for my K75. New elastic straps, new system for mounting the straps, plus some of the inner edges for holding the gasket are gone. I may try the acetone technique to bond new thin brass strips to what is left of the edges.

VIEJO said:

I'm currently at home in Hutto, TX. and the bike is in my barn in Utopia, TX. so it will be a while before I can post any pictures but I'll definitely give it a shot.

Thanks to all responders!

Dave

Click to expand...

Something just occurred to me that may be relevant to the problem.... the PO installed an aftermarket rear shock (Progressive Suspension) which may have changed the air gap between the muffler heat shield and the bottom of the bag.... something to check out when I get back to Utopia.

nil desperandum

jconway607 said:

If I'm not mistaken, I thought that the bags on the K75 bikes could also be used on older R bikes also. I was actually surprised by that, but I seemed to to have seen them on the R bikes. Is it possible that the bags were used on some other heat generating machine other than the K75? These bags seem to move from owner to owner.

I'm currently rebuilding a set of used bags for my K75. New elastic straps, new system for mounting the straps, plus some of the inner edges for holding the gasket are gone. I may try the acetone technique to bond new thin brass strips to what is left of the edges.

Click to expand...

Brackets are/were available to mount the K bags on the mono-shock R bikes from 85 up.

VIEJO said:

Something just occurred to me that may be relevant to the problem.... the PO installed an aftermarket rear shock (Progressive Suspension) which may have changed the air gap between the muffler heat shield and the bottom of the bag.... something to check out when I get back to Utopia.

nil desperandum

Click to expand...

Both the bags and the muffler mount (indirectly) to the frame. They move together without changing the distance between them, so the shock will not change anything.

Jconway has a point. It could have happened on a different bike. Is there any sign of melted plastic or staining on the muffler right where the hole in the bag is?

98lee said:

Both the bags and the muffler mount (indirectly) to the frame. They move together without changing the distance between them, so the shock will not change anything.

Jconway has a point. It could have happened on a different bike. Is there any sign of melted plastic or staining on the muffler right where the hole in the bag is?

Click to expand...

It happened on this bike... PO pointed it out to me and there are traces of burned plastic on the heat shield.

94 K75 Saddlebag repair

VIEJO said:

Something just occurred to me that may be relevant to the problem.... the PO installed an aftermarket rear shock (Progressive Suspension) which may have changed the air gap between the muffler heat shield and the bottom of the bag.... something to check out when I get back to Utopia.

nil desperandum

Click to expand...

Check the current shock length against the stock length.....................

Also I have and old inner bag half laying around that you may have to do the repair. You ship.